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International Journal of Anatomical Variations (2013) 6: 167–169
Case Report
Fourth head of triceps brachii muscle – a case report
Published online September 26th, 2013 © http://www.ijav.org
Preeti SONJE
P VATSALASWAMY
Vasanti AROLE
Department of Anatomy, Padmashree Dr. D. Y. Patil Medical
College Pune, Maharashtra, INDIA.
Dr. Preeti Sonje
Lecturer
Department of Anatomy
Dr. D. Y. Patil Medical College
Pune, Maharashtra, INDIA.
+91 897 5781889
[email protected]
Received September 25th, 2012; accepted March 31st, 2013
Abstract
Variations in the triceps brachii are neither numerous nor common. Each of the heads may be
fused, in varying degrees, with neighboring muscles. During routine dissection of a 65-year-old
male cadaver in the Department of Anatomy, unusual variation of fourth head of triceps brachii
muscle was found. The additional head was seen attached to the upper part of the shaft of humerus
on its medial side close to the surgical neck by a thin, slender tendon and the tendon was passing
over the neurovascular bundle in the radial groove. A small muscle belly was seen extending from
the long tendon and merged with the medial head of triceps. The branch of radial nerve supplying
medial head was seen giving a separate branch to the muscle belly of fourth head.
© Int J Anat Var (IJAV). 2013; 6: 167–169.
Key words [fourth head] [surgical neck] [neurovascular bundle] [radial groove]
Introduction
Anatomical variation of biceps and triceps brachii muscle was
described by many authors. Though the occurrence of four
headed triceps brachii muscle is rare and has been reported
before in literature. Such type of variation was reported
before by Williams et al. and Wood [1]. This additional head
of muscle passing over neurovascular bundle is clinically
important.
Normally triceps brachii muscle has got three heads: long
head, lateral head and medial head. The long head arises from
infraglenoid tubercle of glenoid cavity, the lateral head arises
from posterior surface of shaft of humerus above the radial
groove and the medial head arises from the posterior surface
of shaft of humerus below the radial groove. Sometimes we
get additional head of triceps brachii muscle. In this case we
found an additional head of triceps brachii muscle arising
from posterior surface of shaft of humerus.
Case Report
A long thin and shiny tendon was observed during routine
cadaveric dissection of a 65-year-old male cadaver in the
Department of Anatomy of Padmashree Dr. D. Y. Patil Medical
College Pune, India. The tendon was traced down till the
muscle belly was found. Attachment of the tendon was found
and its nerve supply was traced and photographs were taken.
Variation of fourth head of the triceps brachii muscle was seen
to have clinical significance.
A single tendon was seen being attached to the posteromedial
aspect of upper part of the shaft of humerus close to surgical
neck above radial groove and was running close to medial
side of the shaft of humerus over the neurovascular bundle,
containing radial nerve and profunda brachii artery. Length
of the tendon was about 10 cm and it was very thin (Figure
1).
The tendon was passing over the neurovascular bundle in
the radial groove. Muscle belly was measuring about 7 cm
long and was merging with the medial head of triceps muscle
(Figure 2).
The branch of radial nerve supplying medial head was seen
giving a separate branch to the muscle belly of fourth head
(Figure 3).
Discussion
Normally triceps brachii muscle has three heads: long head,
lateral head and medial head. Long head arises from the
infraglenoid tubercle of scapula, lateral head arises from
posterior surface of shaft of humerus, above the radial groove
while medial head arises from posterior surface of shaft
of humerus below radial groove. In this case extra head of
triceps muscle was seen.
Sonje et al.
168
Ipsilateral four-headed triceps brachii muscle was found by
Tubbs et al. [3]. They reported an additional attachment site
of the medial head of the triceps brachii . This head originated
from the posterior aspect of the surgical neck of the humerus.
Fabrizio and Clemente demonstrated a single tendon arising
from the proximal posteromedial aspect of the shaft of
humerus, distal to the shoulder capsule [4]. The tendon of this
fourth head passed along the medial aspect of the humerus
and gave way to a muscle belly on the medial surface of the
distal one-third of the humerus. The tendon of the fourth head
passed directly over the neurovascular bundle containing
the radial nerve and deep brachial artery at approximately
the point where the neurovascular bundle entered the radial
sulcus.
Triceps brachii muscle show many variations. Each of the
heads may be fused, in varying degrees, with neighboring
NVB
DM
LOHT
FHT
LHT
FHT
Figure 1. Extra tendon of triceps brachii muscle arising from
posteromedial aspect of upper part of the shaft of humerus close
to surgical neck above radial groove. (DM: deltoid muscle; LOHT:
long head of triceps; LHT: lateral head of triceps; FHT: fourth head of
triceps)
Figure 2. The tendon was passing over the neurovascular bundle in
the radial groove. (NVB: neurovascular bundle; FHT: fourth head of
triceps)
muscles. The fibers of the long head may extend to the capsule
of the shoulder joint above or distally, for a greater extent
than usual on the axillary border of the scapula. Macalister
described the variations of triceps brachii as follows [5]:
• It may have a fourth head from the medial part of the
humerus below the head, by a long, slender tendon, and
by an aponeurotic expansion from the capsule of the
shoulder – this head blended with the inner (medial)
head;
• Macalister has frequently seen the long head split, one
attached to the capsule, and the other to the tricipital
spine, axillary border, or the first slip was found splitting
the capsular ligament, like the curved head of rectus
femoris;
• The existence of a slip from the tendon of latissimus dorsi
has been seen several times. It was described by Bergman
in 1855; and it was also mentioned by Halbertsma under
Fourth head of triceps brachii
169
DM
surgical neck of humerus, the muscle belly of extra head was
blending with the long head of triceps brachii muscle [7].
The fourth head of triceps brachii was arising from the upper
part of the posterior aspect of the shaft of the humerus
immediately below the capsule of the shoulder joint. The origin
was by a long tendon which extended on the medial aspect
of arm after crossing the redial nerve and profunda brachii
vessels superficially along with the lateral head of triceps
brachii. In the lower one third of the posterior aspect of the
arm the tendon continued as muscular belly which merged
with the medial part of medial head of triceps brachii [8].
Conclusion
*
Figure 3. The branch of radial nerve supplying medial head was
seen giving a separate branch (asterisk) to the muscle belly of
fourth head.
the name of anconeus quintus; this may occasionally
come from the teres major [5].
A fourth head of triceps may arise from various parts on
humerus, scapula, shoulder joint capsule or coracoid process
[6].
Cheema and Singla also found extra head of triceps brachii
muscle originating from humerus from the medial side of
Relation of extra tendon of triceps brachii muscle passing over
the neurovascular bundle has clinical significance in radial
nerve palsy and arterial compression. Also patients with
weakness and pain in posterior shoulder and arm should be
considered having this variant muscle, which is responsible for
neurovascular compression. Neurovascular compression may
lead to the atrophy of muscles supplied by the neurovascular
bundle. It may compress upon the radial nerve or it can also
compress the ulnar nerve because of its close proximity with
the nerve.
References
[1]
Williams PL, Warwick R, Dyson M, Bannister LH, eds. Gray’s Anatomy. 37th Ed., New York,
Churchil Livingstone. 1989; 615–616.
[2]
Wood J. On human muscular variations in their relation to comparative anatomy. J Anat
Physiol. 1867; 1: 44–59.
[3]
Tubbs RS, Salter EG, Oakes WJ. Triceps brachii muscle demonstrating fourth head. Clin
Anat. 2006; 19: 657–660.
[4|
Fabrizio PA, Clemente FR. Variation in the triceps brachii muscle: a fourth muscular head.
Clin Anat. 1997; 10: 259–263.
[5]
Bergman RA, Afifi AK , Miyauchi R. Illustrated Encyclopedia of Human Anatomic Variation:
Opus I: Muscular System : Alphabetical Listing of Muscles: T, Triceps Brachii. http://
www.anatomyatlases.org/AnatomicVariants/MuscularSystem/Text/T/47Triceps.shtml
(accessed May 2009)
[6]
Anson BJ. Morris’ Human Anatomy. 12th Ed., New York, Mc Graw Hill. 1966; 482–484.
[7]
Cheema P, Singla R. Four headed triceps brachii muscle. Int J Anat Var (IJAV). 2011; 4:
43–44.
[8]
Kulkarni R, Kulkarni RN, Solan S. Unilateral right quadriceps brachii – a case report.
Anatomica Karnataka. 2012; 6: 15–17.